Valve apparatus and method

ABSTRACT

Valve apparatus and method using a valve (gate or ball type) which has one or more seat rings together with means for jacking the rings against the movable valve member. The jacking means is operatively connected to a loading device exterior of the valve body and arranged whereby the jacking force can be relieved to facilitate operation of the valve. Various embodiments are shown involving both manual and automated operation in conjunction with power means for operating the valve.

United States Patent 51 Grove et a1.

[ VALVE APPARATUS AND METHOD [75] Inventors: Marvin H. Grove; Rodney A.

Wailes, both'of Houston, Tex.

[73] Assignees: M & .1 Valve Company; M & .1 Development Company, bothof Houston, Tex.

[22] Filed: Apr. 17, 1972 [21] App]. No.: 244,398

Related US. Application Data [63] Continuation-impart of Ser. No.162,806, July 15,

1971, abandoned.

[52] US. Cl 251/31, 251/62, 251/172, 251/289 [51 Int. Cl. F16k 39/04[58] Field of Search 251/31, 62, 172, 173, 289

[56] References Cited UNITED STATES PATENTS 2,802,483 8/1957 Davis251/31 X 1' if 1 ii I T 3,T790,1 2 3 45] Feb. M5, 1974 2,918,085 12/1959Govan 251/62 X 2,998,220 8/1961 Grieselhuber. 251/31 3,248,879 5/1966Natho 251/31 X 3,464,669 9/1969 Henrion 251/173 3,617,025 11/1971 Gerbic251/172 3,635,436 1/1972 Tillman 251/31 Primary Examiner-Harold W.Weakley ABSIRACT Valve apparatus and method using a valve (gate or balltype) which has one or more seat rings together with means for jackingthe rings against the movable valve member. The jacking means isoperatively connected to a loading device exterior of the valve body andarranged whereby the jacking force can be relieved to facilitateoperation of the valve. Various embodiments are shown involving bothmanual and automated operation in conjunction with power means foroperating the valve.

11 Claims, 7 Drawing Figures PATENTEBFEB 51974 SHEET 1 0F 4 IG. I

PATENTEBFEB 51914 3 "790 123 SHEET Q (If //3 l VALVE APPARATUS ANDMETHOD CROSS-REFERENCE TO COPENDING APPLICATION This application is acontinuation-in-part of our copending application Ser. No. 162,806 filedJuly 15, 1971 (now abandoned).

BACKGROUND OF THE INVENTION Valves are frequently constructed with seatrings carried by the body and surrounding the flow passages. Springs aregenerally provided for urging the rings against the valve member, andthis loading may be supplemented by providing a pressure area which isacted upon by pressure differential between the upstream side of thevalve and the body space, whereby the upstream seat is urged by fluidpressure against the valve member. The seats are frequently providedwith inserts of resilient material to establish an effective seal withthe valve surfaces of the valve member.

Prior valves as described above may require excessive force to movebetween closed and open positions, particularly when the upstreampressure is sufficiently high to cause the upstream seat to be urgedwith considerable force against the valve member. If the pressure areasof the seat are designed to reduce such forces, then leakage may occur.Relatively high loading forces on the seat rings not only cause highoperating forces, but in addition excessive wear and damage to thesealing means when the valve member is moved while such forces areacting on the seat rings. For lower operating pressures the loading onthe seats may be insufficient to prevent some leakage.

- In general, there is need for a valve which will provide adequateloading forces on the seat rings to maintain the desired seal under alloperating conditions, while permitting easy operation of the valvewithout excessive operating forces and without undue wear or injury tothe sealing means carried by the rings.

SUMMARY OF THE INVENTION The present invention relates generally tovalve apparatus and methods of the type used for controlling the flow ofgases and liquids, and particularly to valves and methods that areapplicable for use with relatively high line pressures.

In general, it is an object of the invention to provide a valveapparatus and method which will not require excessive forces to move thevalve member between closed and open positions, but which will provideadequate loading forces on the seat ring or rings during normaloperation to prevent leakage.

Another object of the invention is to provide a valve apparatus andmethod having seat ring loading means exterior of the valve body whichcan be actuated to relieve forces on the seat rings tending to urge themagainst the valve member.

Another object of the invention is to provide a valve apparatus andmethod having hydraulic means for normally applying jacking forces toone or more of the seat rings of the valve, and which has means exteriorof the valve whereby pressure applied to the hydraulic fluid is relievedto facilitate valve operation.

Another object of the invention is to provide a valve apparatus andmethod which automatically reduces loading forces on one or more of theseat rings of the valve when power means connectedto the valve for itsoperating is energized.

Another object of the invention is to provide Valve apparatus and methodwhich makes use of an operator of the double-acting hydraulic type,together with a hydraulic system including a control valve which isoperated to actuate the operator to open and close the valve.Particularly, the invention coordinates the hydraulic system withjacking means for one or more of the seat rings of the valve, wherebyloading forces on the seat rings are automatically relieved when thehydraulic system energizes the hydraulic operator.

Another object of the invention is to provide valve apparatus and methodin means for applying loading force to the seat ring or rings of thevalve is obtained in such a manner that such forces are largelyindependent of line conditions.

In general, the present invention makes use of a valve having a valvemember within a body and movable between open and closed valvepositions. The valve includes at least one seat ring carried by the bodyand surrounding one of the flow passages. The seat ring is provided withmeans adapted to be connected to a loading device exterior of the valvebody which serves to apply jacking forces to the seat ring under normaloperating conditions. When it is desired to move the BRIEF DESCRIPTIONOF THE DRAWING FIG. 1 illustrates a gate valve in end elevation, and inaddition schematically illustrates a hydraulic system for operating thegage valve, together with a loading device serving to apply and relieveloading forces to the seat ring or rings of the valve.

FIG. 2 is a cross-sectional view taken along the line 2-2 of FIG. 1.

FIG. 3 is an enlarged detail in section illustrating the construction ofone of the resilient seal means.

FIG. 4 is an enlarged detail in section like FIG. 3, but showing anothertype of sealing means.

FIG. 5 is a view in section showing the construction of the loadingdevice 21 of FIG. 1.

FIG. 6 illustrates a further embodiment of the invention in which a handpump is employed.

FIG. 7 is a schematic diagram illustrating the component parts of thepump shown in FIG. 7.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The apparatus illustrated inFIG. 1 consists of a valve 10, in this instance one of the gate type,which includes the valve body 11 having aligned flow passages 12 in itsend walls, and a valve gate 13 movable between full open and closedpositions. The valve is shown equipped with a power operator 14 which inthis instance is of the hydraulic type, such as a double-actingcylinder-piston assembly. The operator is directly mounted upon a bonnetassembly 16 which in turn is carried by the upper end of the valve body.The hydraulic pipe connections 17 and 18 to the end portions of thehydraulic cylinder are shown connected to a hydraulic system whichserves to supply liquid under pressure to one or the other of the pipes17 and 18.

The apparatus of FIG. 1 also includes the special hydro-pneumaticloading device 21 and the accumulator 22 which represents a source offluid under pressure. Such accumulators generally consist of a pressurevessel containing gas (e.g., nitrogen) under pressure and a hydraulicfluid, the gas and fluid being separated by a sealed free floatingpiston or elastic diaphram.

Device 21 can be constructed as shown in section in FIG. 5. It consistsof a body 24 which is formed to provide the aligned cylindrical bores25, 26 and 27. The connected plungers 28 and 29 are fitted within thebores 25 and 27, and a somewhat larger piston 31 carried by the plungers28 and 29 is fitted within the bore 26. Suitable sealing means isprovided for the plungers and piston, as for example, sealing means ofthe O-ring type 32 and 33 for the plungers 28 and 29, and means 34 forthe piston 31.

Suitable means can be provided at the ends of the body 24 for lockingthe plungers in a given position. Thus, at the right-hand end shown inFIG. 5, the body is provided with a fitting 35 which is bored to receivethe rod 36 and threaded to receive the screw 37. Rod 36 is sealed withrespect to fitting 35 as by an O-ring. The other end of the body 24 issimilarly provided with fitting 38, rod 39 and threaded screw 40.

The body 24 is also provided with a number of ports for making externalconnections as follows. A port 43 communicates with the space 44 withinthe cylindrical bore 25. A port 45 communicates with the space 46 withinthe cylindrical bore 26 and on the left-hand side of the piston 31. Aport 47 communicates with the space 48 within the cylindrical bore 27.The space 49 I on the right hand side of the piston 31 may be vented tothe atmosphere through duct 51 or breather hole.

The hydraulic connections between the device 21 and the other parts ofthe apparatus are as follows. The port 43 is connected by pipe 53 withone side of the valve 10, as shown in FIG. 1. As will be presentlyexplained, this connection communicates with a hydraulic chamberassociated with at least one of the seat rings of the valve. The port 45is connected by pipe 54 and valve means 55 with what may be termed ashuttle check valve 56. The port 47 is connected by pipe 57 with thepressure tank or flask 22.

Assuming that hydraulic fluid is contained in the space 44 and in thepipe 53 leading to the valve 10, and the tank 22 contains gas andhydraulic fluid at a pressure of, say, 500 p.s.i., then it will beapparent that this pressure is applied to the space 48, thus urging theplungers 28 and 29 toward the left as viewed in FIG. 5. This serves toapply a corresponding pressure to the fluid in pipe 53. Assuming thatfluid pressure is applied to the space 46 to the left of piston 31through pipe 54, then piston 31, together with the plungers 28 and 29,is urged to the right as viewed in FIG. 5, thus relieving the pressureof liquid in pipe 53.

In the apparatus of FIG. 1, fluid pressure is applied from the hydraulicsystem through pipe 54 when fluid pressure is applied to the hydraulicoperator 14 for operation of the valve. The hydraulic fluid systemschematically illustrated in FIG. 1 consists of a four-way control valve61 which connects to pipe 62 that supplies fluid under pressure, andpipe 63 through which liquid is exhausted. Preferably, valve 61 is soconstructed that its operating member is spring biased to anintermediate normal position. Pipes 17 and 18 leading from the cylinderof the hydraulic operator 14 make direct connection with ports of thefour-way valve 61.

The shuttle check valve 56 as schematically illustrated consists of twospaced seats nd a single check ball. Pipes 64 and 65 connect the seatports with the pipes 17 and 18. The valve means 55 as schematicallyillustrated is of the three-way pressure operated type. Pipe 54 connectswith one port of the three-way valve, and the other two ports connectwith pipes 67 and 68. Pipe 68 connects directly with pipe 69, which inturn connects with the shuttle check 56 at a point between the seats.Pipe 67 includes a check valve 71 which allows flow from shuttle valve56 to the three-way valve 55 but prevents flow in the reverse direction.

A fluid pressure operator 72 has its piston or other fluid pressureoperating member connected to the operating member of the three-wayvalve 55. Also, valve 55 is normally biased to one of its two operatingpositions as by a spring 73. The position to which it is spring biasedis such that pipes 68 and 54 are placed in communication. When operator72 is actuated by application of fluid pressure, valve 55 is moved toits other operating position in which pipes 67 and 54 are incommunication.

FIG. 2 illustrates a suitable type of valve sealing means which can beused with the apparatus. In this instance the end walls 74 of the valvebody, which are welded to the side walls 75, are bored to accommodatethe seat rings 76. These rings surround the aligned flow passages 12.The seat rings have stepped diameters 77 and 78 which are fitted withinthe cylindrical bores 79 and 81 that are machined in the end walls 73.Each seat ring is sealed with respect to the body by the seat rings 82and 83 of the resilient O-ring type. The end face of each seat ring 76,which is adjacent the gate 13, is provided with sealing assemblies 84and 85 which may be similar in construction, or somewhat different asillustrated. Assembly 84 is similar to that disclosed and claimed incopending application Ser. No. 17,365, filed Mar. 9, 1970. Briefly, itconsists of an annular member 86 together with a more resilient member87 made of suitable material such as synthetic rubber or elastomer.These parts are fitted within the annular recess 88 in the seat ring 76,whereby the annular member 87 is in radial compression and has its edgeface in sealing engagement with the adjacent valve surface of the gate13.

The assembly 85 as illustrated in FIG. 2 is likewise disclosed in saidcopending application Ser. No. 17,365. It consists of an annular member89 made of suitable non-metallic material like nylon, together with twoannular members 91 and 92 which are made of more resilient material suchas synthetic rubber or elastomer. These parts are disposed within theannular recess 93 with the resilient members 91 and 92 in radialcompression. The edge faces of members 91 and 92 engage and form sealswith respect to the adjacent surface of gate 13. The sealed off space 94between the concentric areas of sealing contact between members 91 and92, and the gate 13 is shown connected by duct 95 to a fitting 96, whichin turn may be connected to a titting on the exterior of the valve body.Such an arrangement can be used to determine if the sealing assembly 85is leaking. Thus, if duct 95 is vented to the atmosphere and then closedat the exterior of the valve, a build-up of pressure will indicateleakage past one or the other of the resilient members 91 or 92.

A plurality of circumferentially disposed compression springs 97 areprovided to apply a nominal loading force to each of the seat rings,thereby urging these rings against the gate 13. The closed annularchambers 98 provided between the resilient O-rings 82 and 83 for eachseat ring communicates with a duct 99that connects to exterior fittings101 and 102. In some instances, one or the other of these fittings maybe separately connected to the pipe 53, but generally they are connectedtogetheras by pipe 103 and thence to the pipe53. In other words,application of fluid under pressure to pipe 53 serves to apply the fluidto both of the annular chambers 98.

It will be apparent that application of fluid under pressure to thechambers 98 of the seat rings serves to load or hydraulically jack theserings against the gate, the jacking forces being proportionate to theapplied fluid pressure. The jacking force can be such that the resilientsealing assemblies 84 and 85 are compressed to the point of directmetal-to-metal contact between the seat rings and the gate.

While the particular sealing means described above is effective, othertypes of sealing assemblies can be used which have provision forapplying fluid pressure to one or both of the assemblies to cause metalseat rings to be tightly clamped against the valve member,

Operation of the apparatus shown in FIG. 1 isas follows. Normally, thefluid pressure in pipe 53 is maintained at a value sufficient tohydraulically load or jack the seat rings 76 with the desired forceagainst the gate 13. This fluid pressure is maintained by the plunger 28and by the plunger 29 which urges plunger 28 towardthe left as viewed inFIG. 5 under the urge of fluid pressure loading from the accumulator 22.

Assuming that the jacking forces are sufficiently high to effectmetal-to-metal contact between the seat rings and the gate, the gate isheld firmly by the seat rings, and relatively high forces would berequired to move the gate from one position to another. Assuming thatthe gate is thus locked in open position and it is desired to close thevalve, the four-way control valve 61 is moved from its normal neutralposition to a position in which hydraulic fluid is supplied underpressure to pipe 17, and to exhaust fluid through the control valve frompipe 18. As hydraulic fluid is first applied to pipe 17, initialpressure developed which is applied through pipe 64 to shuttle valve 56whereby the latters valve member is urged against its left hand seat andfluid pressure is applied through pipe 69 to the operator 72. Thisoperator is thus energized to operate valve 55 against the urge ofspring 73 whereby pipe lines 67 and 54 are placed in communication tocause fluid pressure to be applied to the space 46 on the left hand sideof piston 31. The force thus acting upon piston 31 is in opposition tothe loading plunger 29 and the force applied urgingpiston 31 to theright may be about equal to or slightly greater than the loading appliedto the plunger 29 by virtue of fluid under pressure in chamber 48. Thus,before the hydraulic operator 14 has moved the gate, the hydraulicpressure applied to the seat rings is relieved, and the jacking orloading forces urging these seat rings against the gate greatly reducedor completely relieved, thus freeing the gate for movement. Thereafterthe operator 14 continues to move the gate to the close position. Whenthis position is reached, control valve 61 is returned to its neutralposition in which lines 17 and 18 are both connected through the controlvalve with the exhaust line 63. Fluid from space 46 may now vent throughpipe 54, three-way valve 55, pipe 68, shuttle valve 56, pipe 64 andcontrol valve 61; thus the loading-in space 48 is again effective toapply fluid pressure through pipe 53 to lock the gate.

Assuming now that it is desired to return the gate to its first or openposition, then the four-way valve 61 is again operated from its-neutralposition to supply fluid under pressure to pipe 18, with fluid beingexhausted through pipe 17. Again, the initial pressure applied to pipe18 is transmitted through shuttle valve 56, threeway valve 55 and pipe54, with the result that this liquid pressure is appliedto space 46 ofdevice 21 to again urge the piston 31 toward the right as viewed in FIG.5. Thus, the jacking forces upon the seat rings are again relievedbefore the gate is moved and during movement back to open position.

If during a cycle of operation control valve 61 is moved to neutralposition to stop the gate in an intermediate position, fluid is againvented through pipe 54 to apply locking pressure through pipe 53.

In some instances it is desirable to lock the plungers 28 and 29 in oneposition, whereby hydraulic loading pressure is either-maintained inline 53, or application of jacking pressure is prevented. Thus, bymanipulation of the screw 40 shown on the left hand end of the body 24in FIG. 5, the screw 40 can be advanced to cause rod 39 to engage theend of the plunger 28, thus preventing movement of this plunger in adirection to apply pressure to liquid in .pipe 53, or moving the plungera short distance to relieve pressure in pipe 53. Likewise, if it isdesired to retain loading pressure in pipe 53, screw 37 is advanced-tocause rod 36 to engage the plunger 29 and urge this plunger withsufficient force toward the left that it applies the requisite pressureto the pipe 53. When the screw 38 is advanced as just described,the'maintenance of hydraulic jacking pressure in pipe 53 isindependentof hydraulic loading by way of accumulator 22.

The apparatus described above in connection with FIG. 1 is also suitablefor use where a central hydraulic system is arranged to operate aplurality of valve operators. In such event, one pressure tank may servea'll'of the valves. Each valve, however, will be provided with itsindividual control valve, three-way valve 55 and load controlling device21.

A further simplified apparatus has been illustrated in FIG. 6. In thisinstance, the load controlling device 103 is the same as in FIG. 5.However, a hand-operated hydraulic pump 111 has been substituted forconnection to the hydraulic operating system. The pump is shown havingits pressure pipe 112 directly connected to the port 106. It has a handoperating lever 113 and a cylinder 114 for developing the desiredpressure in the pipe 112. A pump schematic is shown in FIG.- 8. The pumpintake check valve 116 is located within the-liquid reservoir 117. Thebypass device 118 likewise located in the reservoir serves to limit thedeveloped discharge pressure. Check valve 119 serves to lock thepressure in the line 112. Manually operated valve 121, likewiseindicated in FIG. 7, may be operated to relieve thev pressure in line112.

It will be evident that with the apparatus shown in I FIG. 7, andassuming that the pipe 53 is connected to a valve in the same manner asin FIG. 1, the plunger assembly normally will maintain pressure withinline 53 to retain the seat rings tightly pressed against the valvemember. However, when it is desired to relieve the jacking forces on theseat rings, the hand pump 111 is operated to develop pressure in line112, whereby this pressure acting upon the piston 31 serves to relievethe pressure in line 53, thus releasing the seat rings.

We claim:

1. In valve apparatus, a valve body having aligned flow passages, avalve member within the body and movable between open and closedpositions relative to the flow passages,at least one seat ring movablycarried by the body and surrounding one of the flow passages, meansadapted to receive hydraulic fluid under pressure for jacking the ringagainst the valve member, a loading device exterior of the valve membercomprising a body, a cylinder formed in the body, a plunger fitted inthe cylinder,'the cylinder being adapted to contain hydraulic fluid, afluid connection between said cylinder and the first-named means,loading means for yieldably urging the plunger in a direction to applyhydraulic fluid under pressure to the first means, and'controllablemeans for opposing the urge of said last named means.

2. The valve apparatus as in claim 1 in which said loading meansconsists of a second cylinder, a second plunger fitted in the secondcylinder, the second plunger being mechanically connected to the firstnamed plunger, and a source of fluid pressure connected to the secondcylinder to urge the second plunger in a direction to urge the firstnamed plunger against the hydraulic fluid.

3. Apparatus as in claim 1 together with mechanical means for lockingthe plunger in a desired position.

4. Apparatus as in claim 1 together with power means adapted to beenergized for moving the valve member between open and closed positions,and means responsive to energization of said power means for opposingthe urge of said loading means.

5. Apparatus as in claim 4 in which said power means is of the hydrauliccylinder-piston type together with a hydraulic system for supplying andexhausting fluid from the operator, and in which the means for opposingthe urge of said loading means includes hydraulic actuating meansmechanically connected to the first named plunger and means forming afluid connection between said hydraulic actuating means and thehydraulic system whereby when the power operator ishydraulicallyenergized to move the valve member between open and closedpositions, hydraulic fluid is supplied to said hydraulic operator tooppose the urge of said loading means.

6. In valve apparatus, a valve body having aligned flow passages, avalve member within the body and movable between open and closedpositions relative to the flow passages, at least one seat ring movablycarried by the body and surrounding oneof the flow passages, meansadapted to receive hydraulic fluid under pressure for jacking the ringagainst the valve member, and a device exterior of the valve membercomprising a body, a first cylinder formed in the body, a first plungerfitted in the cylinder, the cylinder being adapted to contain hydraulicfluid, a fluid connection between said cylinder and the first namedmeans, said device also including a second cylinder, a second plungerfitted within the second cylinder and directly connected to the firstplunger, the second cylinder being adapted to have fluid connection witha source of fluid under pressure to apply loading force to both of theplungers, a third cylinder formed within the body of said device, apiston fitted in the third cylinder and directly connected with saidplungers, said third cylinder being adapted to be connected with acontrollable source of fluid under pressure whereby fluid under pressureapplied to said third cylinder opposes the loading force applied to saidplungers.

7. Apparatus as in claim 6 together with mechanical means for lockingthe plungers in a desired position.

8. Valve apparatus as in claim 6 together with a power operator adaptedto be energized to move the valve member between closed and openpositions, and means for supplying fluid under pressure to said thirdcylinder when said power operator is energized.

9. Valveapparatus as in.claim 6 together with a hydraulic power operatorof the cylinder-piston type adapted to be energized by application ofhydraulic fluid under pressure to move thevalve member between closedand open positions, a hydraulic system connected with said operator andadapted to supply and exhaust hydraulic fluid from the same, said systemincluding a control valve adapted to be moved between operatingpositions whereby the operator is caused to move the valve memberbetween closed and open positions, and means forming a fluid connectionbetween said third cylinder and said hydraulic system whereby when saidsystem is controlled to cause the hydraulic operator to be energized,fluid pressure is applied to said third cylinder to oppose the urge ofsaid loading means.

10. Apparatus as in claim 9 together with means for limiting the maximumpressure of hydraulic fluid supplied to said third cylinder.

11. Apparatus as in claim 9 in which said last means includes a threeway valve and pressure operated means for positioning said valve, saidvalve serving to permit fluid pressure from the hydraulic system to beapplied to said third system or'vented from the same.

1. In valve apparatus, a valve body having aligned flow passages, avalve member within the body and movable between open and closedpositions relative to the flow passages, at least one seat ring movablycarried by the body and surrounding one of the flow passages, meansadapted to receive hydraulic fluid under pressure for jacking the ringagainst the valve member, a loading device exterior of the valve membercomprising a body, a cylinder formed in the body, a plunger fitted inthe cylinder, the cylinder being adapted to contain hydraulic fluid, afluid connection between said cylinder and the first named means,loading means for yieldably urging the plunger in a direction to applyhydraulic fluid under pressure to the first means, and controllablemeans for opposing the urge of said last named means.
 2. The valveapparatus as in claim 1 in which said loading means consists of a secondcylinder, a second plunger fitted in the second cylinder, the secondplunger being mechanically connected to the first named plunger, and asource of fluid pressure connected to the second cylinder to urge thesecond plunger in a direction to urge the first named plunger againstthe hydraulic fluid.
 3. Apparatus as in claim 1 together with mechanicalmeans for locking the plunger in a desired position.
 4. Apparatus as inclaim 1 together with power means adapted to be energized for moving thevalve member between open and closed positions, and means responsive toenergization of said power means for opposing the urge of said loadingmeans.
 5. Apparatus as in claim 4 in which said power means is of thehydraulic cylinder-piston type together with a hydraulic system forsupplying and exhausting fluid from the operator, and in which the meansfor opposing the urge of said loading means iNcludes hydraulic actuatingmeans mechanically connected to the first named plunger and meansforming a fluid connection between said hydraulic actuating means andthe hydraulic system whereby when the power operator is hydraulicallyenergized to move the valve member between open and closed positions,hydraulic fluid is supplied to said hydraulic operator to oppose theurge of said loading means.
 6. In valve apparatus, a valve body havingaligned flow passages, a valve member within the body and movablebetween open and closed positions relative to the flow passages, atleast one seat ring movably carried by the body and surrounding one ofthe flow passages, means adapted to receive hydraulic fluid underpressure for jacking the ring against the valve member, and a deviceexterior of the valve member comprising a body, a first cylinder formedin the body, a first plunger fitted in the cylinder, the cylinder beingadapted to contain hydraulic fluid, a fluid connection between saidcylinder and the first named means, said device also including a secondcylinder, a second plunger fitted within the second cylinder anddirectly connected to the first plunger, the second cylinder beingadapted to have fluid connection with a source of fluid under pressureto apply loading force to both of the plungers, a third cylinder formedwithin the body of said device, a piston fitted in the third cylinderand directly connected with said plungers, said third cylinder beingadapted to be connected with a controllable source of fluid underpressure whereby fluid under pressure applied to said third cylinderopposes the loading force applied to said plungers.
 7. Apparatus as inclaim 6 together with mechanical means for locking the plungers in adesired position.
 8. Valve apparatus as in claim 6 together with a poweroperator adapted to be energized to move the valve member between closedand open positions, and means for supplying fluid under pressure to saidthird cylinder when said power operator is energized.
 9. Valve apparatusas in claim 6 together with a hydraulic power operator of thecylinder-piston type adapted to be energized by application of hydraulicfluid under pressure to move the valve member between closed and openpositions, a hydraulic system connected with said operator and adaptedto supply and exhaust hydraulic fluid from the same, said systemincluding a control valve adapted to be moved between operatingpositions whereby the operator is caused to move the valve memberbetween closed and open positions, and means forming a fluid connectionbetween said third cylinder and said hydraulic system whereby when saidsystem is controlled to cause the hydraulic operator to be energized,fluid pressure is applied to said third cylinder to oppose the urge ofsaid loading means.
 10. Apparatus as in claim 9 together with means forlimiting the maximum pressure of hydraulic fluid supplied to said thirdcylinder.
 11. Apparatus as in claim 9 in which said last means includesa three way valve and pressure operated means for positioning saidvalve, said valve serving to permit fluid pressure from the hydraulicsystem to be applied to said third system or vented from the same.